This invention relates to multi-layer protective fabrics.
Garments used in fire fighting, for example, are made of fabrics that not only protect the fire fighter from the heat and flame of the fire, but also are waterproof and allow water vapor to pass from inside to outside the garment.
One such fabric is a laminate of a first layer comprising rayon and NOMEX (a fire-retardant, high-strength woven or non-woven fibrous material available from duPont) and a second layer of a micro-porous urethane film (e.g., P55FR available from Porvair of King""s Lynne, UK). A micro-porous material is, for example, one that has pores sized to permit vapor molecules to pass, while blocking water molecules. The urethane film, which is normally flammable, is made fire retardant by loading it with fire retardant components during manufacture by a solvent process.
The National Fire Protection Agency (NFPA) recently changed its published standards to require fire fighting garments also to resist penetration by any of a list of chemicals sprayed in a specified way against the surface of the garment.
One attempt to meet the new standard involved coating the micro-porous urethane film of the fabric described above with a chemical resistant coating.
In general, in one aspect, the invention features a multi-layer protective fabric in which a breathable barrier film blocks a liquid chemical while permitting moisture vapor to pass through it. The film is thinner than 1 mil and contains a fire retardant component. Layers are bonded on both sides of the film by fire retardant adhesive.
In general, in another aspect of the invention, a multi-layer protective fabric includes a thin urethane film, a flame-retardant fibrous layer, and a flame-retardant micro-porous urethane layer. The film includes flame-retardant additives, blocks a liquid chemical from passing through it, and breathes by an absorption/de-sorption process to permit water vapor to pass through it. The fibrous layer is bonded on one surface of the film. The micro-porous urethane layer is bonded on the other surface of the film.
Implementations of the invention may include one or more of the following features. The urethane film may have a thickness in the range of 0.1 to 1 mils, preferably 0.15 to 0.25 mils, e.g., about 0.2 mils thick. Adhesive may bond the urethane film to at least one of the fibrous layers or the micro-porous layer. The adhesive may be distributed in a pattern in which at least 75%, preferably at least 85%, most preferably at least 90% of the film is free of adhesive. The adhesive may contain flame-retardant components. The fibrous layer may include NOMEX, Kevlar, or PBI. The micro-porous urethane layer (e.g., PORVAIR) may include flame-retardant components.
In general, in another aspect of the invention, a multi-layer fabric includes a sandwich that has a core and layers bonded on the core. The core has a weight per square meter less than 2xc2xd grams and is impenetrable by a liquid chemical and breathable to water vapor. The fire-retardant layers are bonded on each side of the core, at least one of the fire-retardant layers being penetrable by the liquid chemical, impenetrable by water, and breathable to water vapor.
Among the advantages of the invention may be one or more of the following.
The fabric meets NFPA standards for flame-retardancy and chemical resistance while being waterproof and breathable. A fabric of the required characteristics can be produced repeatably and predictably. The fabric is relatively inexpensive to make. The polyethylene-backed film is easily stored and shipped and manipulated during the lamination process. The barrier properties of the film are maintained prior to the lamination process.
Other advantages and features will become apparent from the following description, and from the claims.